The subject matter disclosed herein relates to gas turbines, and more particularly to a gas turbine inner flow path cover piece.
FIG. 1 illustrates a prior art gas turbine configuration 100. In typical hot gas section designs, such as the configuration 100, turbine wheels 105, 110, including airfoil slots 101, are not designed to withstand the high temperatures of the combustion gas within the turbine. Gaps between stationary and rotating parts could cause this gas to reach the wheel materials and cause them to require excess maintenance. As such, cooler air is introduced into a cavity 115 in between wheels 105, 110 that pressurizes the cavity 115, preventing hot air from leaking into the cavity 115. A diaphragm 121 is typically included to fill the cavity 115. The process of introducing the cooler air is referred to as cavity purging. Cavity purging implements pressurized air that leaks into the hot gas path in the gas turbine, thereby reducing the efficiency of the gas turbine.
Current solutions implement direct purging of air into the cavities between the rotor wheels. Other solutions implement an intermediate wheel that carries a platform to seal the hot gas path away from the wheel surfaces. Current solutions can incur a penalty in engine performance due to the parasitic use of compressor air to purge the cavities as to avoid ingestion. Also, the cavities eject air perpendicular to the main flow path, incurring mixing losses before the gas enters the blade or nozzle row.